As portable communication terminals (for example, smart phones or tablet terminals) become highly functional and video contents become higher in density (high density), communication terminals are generally used to transmit and receive high image quality video files or large capacity files. For this reason, a communication terminal is required to transmit and receive large capacity files at high speed to and from the communication terminal of a destination communication party (hereafter simply referred to as “destination terminal”).
As a high-speed communication method, short-distance wireless communication using a millimeter wave band is attracting attention. The millimeter wave communication enables wireless communication at a throughput on the order of Gbps or higher and is used, instead of infrared communication, as direct communication between a communication terminal and a destination terminal, thereby being expected as a communication method for reducing traffic on public wireless network.
In order that the millimeter wave communication is used widely in the future, the millimeter wave communication is required to coexist with wireless LAN (Local Area Network) communication that is used widely at present, and communication terminals are expected to use both the millimeter wave communication and the wireless LAN communication.
In comparison with the wireless LAN communication, in the millimeter wave communication, communication can be performed at high speed, but the communication distance is short and the directivity is strong. In other words, in comparison with the wireless LAN communication, in the millimeter wave communication, the throughput during wireless communication changes significantly and communication is disconnected depending on the usage of the communication terminal; for these reasons, the cooperation between the millimeter wave communication and the wireless LAN communication during communication, in particular, seamless switching therebetween, is thought to be important.
For example, in IEEE (The Institute of Electric and Electronics Engineers, Inc.) 802.11ad serving as the standard for 60 GHz band millimeter wave communication, the FST (Fast Session Transfer) technology has been standardized as a system for performing seamless and bidirectional communication path switching between the millimeter wave communication and the wireless LAN communication of a 5 GHz band or a 2.4 GHz band, that is, as a system for performing switching from the millimeter wave communication to the wireless LAN communication or from the wireless LAN communication to the millimeter wave communication. The FST technology is attracting attention as the standard for complementing the features of the millimeter wave communication.
In the communication of a communication terminal capable of performing the millimeter wave communication and the wireless LAN communication, by minimizing the overhead in the case that the millimeter wave communication is switched to the wireless LAN communication, the non-communication state in the case that the millimeter wave communication was disconnected can be minimized, whereby the high-speed performance of the millimeter wave communication can be utilized effectively. Furthermore, in the communication in which the communication terminal capable of performing the millimeter wave communication and the wireless LAN communication uses the FST technology, it is also necessary to consider power saving in data communication.
In a state in which a plurality of communication paths are available, as a method for switching the communication paths depending on a communication task (for example, file transfer), for example, the communication apparatus of Patent Document 1 is known (refer to FIG. 9). The communication apparatus of Patent Document 1 will be described later referring to FIG. 9.